1. Field
Embodiments relate to a method of evaluating luminance of a light source and a lighting apparatus.
2. Background
Group III-V compound semiconductors, such as GaN, AlGaN, etc., are widely used for optoelectronics and electronics because of several advantages, such as, for example, easily controllable wide band gap energy.
In particular, light emitting devices, such as Light Emitting Diodes (LEDs) or Laser Diodes (LDs), which use group III-V or group II-VI compound semiconductors, are capable of emitting visible and ultraviolet light of various colors, such as red, green, and blue, owing to development of device materials and thin film growth techniques. Moreover, these light emitting devices are capable of emitting white light with high luminous efficacy through use of a fluorescent substance or color combination, and have advantages of low power consumption, semi-permanent lifespan, fast response time, safety and environmental friendliness as compared to conventional light sources, such as fluorescent lamps, incandescent lamps, etc.
Accordingly, application sectors of light emitting devices are expanded up to transmitting modules of optical communication means, LED backlights to replace Cold Cathode Fluorescence Lamps (CCFLs) which serve as backlights of Liquid Crystal Display (LCD) apparatuses, white LED lighting apparatuses to replace fluorescent lamps or incandescent lamps, head lights of vehicles and traffic lights.
Lighting apparatuses or car headlamps may include a light emitting device package in which a plurality of light emitting devices is disposed in a single unit.
Luminance is an important factor in terms of product characteristics of lighting apparatuses or headlamps. In particular, there is increasing needs for lighting apparatuses or headlamps having good luminance uniformity.
Currently, minimum and maximum values of luminance data are utilized as criteria of luminance uniformity of lighting apparatuses, for example. However, the aforementioned minimum and maximum values of luminance data indicate only minimum and maximum values of luminance in each area of a single lighting apparatus, and do not indicate the average of the entire lighting apparatus.
In addition, a deviation of each area with respect to the average luminance of the entire lighting apparatus is an important factor to determine luminance uniformity, but may not be represented using only minimum and maximum values of luminance in each area.
Moreover, the lighting apparatus has lower luminance in an edge area thereof than that in a central area thereof, which may have an effect on the above-described minimum value of luminance in each area.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.